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1.
Large volume of iron oxy-hydroxide minerals occur in association with manganese oxide phase in manganese ores of the Eastern Ghats Supergroup, Koraput district, Orissa. On the basis of OH content, the iron mineral can be classified into hydrohematite, goethite, and hydrogoethite. These minerals exhibit eight types of microstructures such as ooloidal, caterpillar, disseminated, reniform, worm, mosaic, globular and spherulitic. Chemical composition of such micro-structures obtained through EPMA, distinguishes them into three domains, developed under different environment. Hydrohematite, having 8–10 % H2O, characteristically contains higher pc of manganese (>5%) and phosphorous (>0.6%) but have low silica and alumina. These are formed syngenetically with Mn-oxide minerals in a manganese rich paragenesis. Goethite containing 11 to 12% water, has relatively low level of manganese and phosphorous, and formed in a later period, as secondary open space filling. Hydrogoethite shows very high water content (>16%), almost devoid of manganese, and impoverished in phosphorous but having higher percentage of alumina, silica and appreciable copper and nickel. This was latest to form in the zone of oxidation under supergene condition.  相似文献   

2.
Iron ore deposits are generally described in terms of size, grade and chemical composition rather than the mineralogical and microstructural characteristic of different ore types. It is essential, however, to know the morphology, microstructure and chemical composition of individual minerals for optimum mineral processing. Goethite is reported to occur as a ubiquitous phase in many iron ore types and is particularly abundant in the Precambrian banded iron ore formation of north Orissa, India. Goethite from the Bonai–Keonjhar Belt in Orissa has been examined in terms of its morphology and microstructure in relation to chemical composition. Electron microscopy indicated several goethite morphotypes including botryoidal, nodular, spheroidal, platy, stalactitic and flaky. These different morphotypes display intergranular, intragranular, wedge, reniform, comb, prismatic, cavity-line and bead microstructures. In situ analysis using electron probe microanalyzer indicated a wide compositional variation among the different morphotypes and microstructures. Goethite replacing hematite is generally devoid of deleterious elements while re-precipitated goethite generally contains adsorbed alumina, silica and/or phosphorus. Nodular goethite commonly has a high phosphorus level while botryoidal, spheroidal and platy goethite often contains increased combined alumina and silica. Goethite having a reniform, wedge, intergranular or intragranular microstructure is highly water bearing and cryptocrystalline in nature. During dehydration, bead, comb, cavity-lined or prismatic goethite develop, which are more crystalline and which have a higher iron concentration. Goethite with a wedge, prismatic or bead-type microstructure has a higher adsorption of silica (2–4%), while goethite having an intergranular, bead or prismatic microstructure invariably contains appreciable phosphorus, generally at levels deleterious to processing.  相似文献   

3.
Direct reduction of iron ore to produce electric furnace feed for steelmaking is becoming economically important on a worldwide scale. For this application an iron ore superconcentrate containing less than 2% silica is demanded. Pilot plant and commercial operations have shown that high-intensity wet magnetic separation is well adapted to meet this specification with high recovery and attractive capital and operating costs. Tests with the Jones separator have produced superconcentrates containing less than 1.5% silica with over 90% iron recovery from preconcentrates produced by sizing or by gravity or low-intensity magnetic separation. Estimated total capital and operating costs to produce a ton of superconcentrate by high-intensity wet magnetic separation are $0.43 for retreatment of specular hematite spiral concentrate, $0.47 for Brazilian hematite fines, and $0.49 for magnetite.  相似文献   

4.
Precambrian iron ores of the Singhbhum-North Orissa region occur in eastern India as part of the Iron Ore Group (IOG) within the broad horse-shoe shaped synclinorium. More than 50% of Indian iron ore reserves occur in this region. Massive-hard, flaky-friable, blue dust and lateritic varieties of iron ores are the major ore types, associated with banded hematite, jasper and shales. These ores could have formed as a result of supergene enrichment through gradual but extensive removal of silica, alumina and phosphorus from banded iron formations and ferruginous shale. Attempts for optimal utilization of these resources led to various ore characterization studies using chemical analysis, ore and mineral petrography, XRD analysis, SEM and electron probe micro analysis (EPMA). The ore chemistry indicates that the massive hard ores and blue dust have high iron, low alumina and phosphorus contents. Because of high quality, these ores do not require any specialized beneficiation technique for up-gradation. However, flaky-friable, lateritised and goethitic ores are low in iron, high in alumina and phosphorus contents, requiring specific beneficiation techniques for up-gradation in quality. XRD, SEM and ore microscopic studies of massive hard ores indicate the presence of hematite and goethite, while flaky and lateritic ores show a higher concentration of goethite, kaolinite, gibbsite and hematite. EPMA studies show the presence of adsorbed phosphorous as fine dust in the hard ores. Sink and float studies reveal that most of the gangue minerals are not completely liberated in the case of goethitic and lateritic ores, even at finer fractions.  相似文献   

5.
Phase assemblages and phase compositions were studied experimentally in water-saturated, biotite-bearing peraluminous granitic melts as a function of alumina excess and temperature. The runs were performed at 2 and 5 kbars under NNO buffer. Biotite was stable only in composition containing 5% of normative corundum; it coexisted with cordierite and hercynite at 2 kbars and with hercynite at 5 kbars. In composition containing 10% of normative corundum biotite was not observed; abundant cordierite and hercynite were the only Fe-Mg-Al minerals. These relationships show that, at constant pressure, the amount of cordierite increases with increasing excess of alumina. Simultaneously the stability of biotite decreases due to preferential partitioning of Mg into cordierite and Fe into biotite. Besides the distribution of Fe, Mg and Al among the coexisting solid phases, solubility of these elements in the melts is given. Below 900° C melts are poor in iron and magnesium and correspond, in terms of these elements, to leucogranites. It is suggested that the leucogranitic magmas, such as parental magmas of European Hercynian and Himalayan leucogranites, must have been formed through highly efficient separation of partial melt from restite, in which ferromagnesian components are concentrated. Peraluminous granites rich in ferromagnesian minerals originate supposedly from restite-bearing magmas.  相似文献   

6.
A large deposit of low-grade kaolinite is occurring within the rocks of Lower Vindhyan Supergroup southwest of Chittaurgarh, Rajasthan. The deposit is being utilised by open-cast, manual to semi-mechanised methods of mining. Kaolinite produced is being marketed without processing. Earlier, nearly 60% of the kaolinite produced from the area was consumed by cement industries, but in recent past, utilisation of low-grade kaolinite has been minimised by cement industries in production of ordinary cement and hence its production has significantly declined. Mineralogical studies reveal that kaolinite is the main clay-mineral and quartz, calcite, iron-oxides and biotite are present as non-clay minerals in clay deposit of the area. Chemical analysis of the kaolinite show that alumina ranges from 15 to 35% while, silica and iron varies from 51 to 78% and 0.25 to 2.50% respectively.  相似文献   

7.
Natural organic matter is readily adsorbed by alumina and kaolinite in the pH range of natural waters. Adsorption occurs by complex formation between surface hydroxyls and the acidic functional groups of the organic matter. Oxides with relatively acidic surface hydroxyls, e.g. silica, do not react strongly with the organic matter. Under conditions typical for natural waters, almost complete surface coverage by adsorbed organic matter may be expected for alumina, hydrous iron oxides and the edge sites of aluminosilicates. Potentiometric titration and electrophoresis indicate that most of the acidic functional groups of the adsorbed organic matter are neutralized by protons from solution. The organic coating is expected to have a great influence on subsequent adsorption of inorganic cations and anions.  相似文献   

8.
This study investigated the performance of electrocoagulation using iron and aluminum electrodes for removing silica, calcium and magnesium from cooling tower blowdown and reverse osmosis reject waters. Experiments were conducted at both the bench and pilot scales to determine the levels of target species removal as a function of the coagulant dose. At the bench scale, aluminum removed the target compounds from both cooling tower blowdown and reverse osmosis reject more efficiently than iron. A 2 mM aluminum dose removed 80 % of the silica and 20 to 40 % of the calcium and magnesium. The same iron dose removed only 60 % of the silica and 10 to 20 % of the calcium and magnesium. When operated with iron electrodes, pilot unit performance was comparable to that of the bench unit, which suggests that such systems can be scaled-up on the basis of coagulant dose. However, when operated with aluminum electrodes the pilot unit underperformed the bench unit due to fouling of the electrode surfaces after a few hours of operation. This result was completely unexpected based on the short-term experiments performed using the bench unit.  相似文献   

9.
地质样品正构烷烃组分分离纯化的部分问题探究   总被引：3，自引：3，他引：0  
用实验室自配的标准正构烷烃样品分别经硅胶或氧化铝柱层析后发现,等量溶剂洗脱的情况下硅胶对长链正构烷烃无吸附而氧化铝具有一定吸附性。进一步通过用植物样品测试4种层析柱填充方法,发现不论是只用氧化铝填充还是上部硅胶下部氧化铝和上部氧化铝下部硅胶,都会对长链正构烷烃产生一定的吸附,且这种吸附效果随着碳链的增长而增强。在实验条件下,当碳链加长到C36时,用硅胶加氧化铝填充层析柱的吸附量已达到20%左右,而只用氧化铝填充层析柱的吸附量则高达50%。故建议对研究高碳数正构烷烃的地质样品组分提取时用单一的硅胶柱层析方法。同时,实验显示对于一些杂质多的正构烷烃样品经过尿素络合后比络合前"干净"得多。18个黄土-古土壤和植物样品平均回收率为50%左右,经过尿素络合后的样品正构烷烃各组分相对含量基本不会发生改变,也不会产生明显的同位素分馏效应。因此在进行非正构组分干扰较大的正构烷烃各组分相对含量或同位素分析时,可以选择尿素络合的方法来将其纯化。  相似文献   

10.
On the Occurrence of Silician Magnetites   总被引：2，自引：0，他引：2  
Abstract: About 120 specimens of magnetite from various localities are examined by an electron microprobe analyzer. Magnetites containing more than one weight percent of silica but lack of any other components than ferrous and ferric iron, called silician magnetites in the present paper, are recognized in 23 skarn, one vein and one thermally metamorphosed massive sulfide deposits. Thus it is confirmed that this mineral occurs in nature much more frequently than so far expected. Besides silician magnetites, magnetites with appreciable amounts of Al2O3, CaO, MgO and other components along with silica, are also recognized in some skarn deposits. Magnetites with such unusual compositions are found only in hydrothermal environments, and it is suggested that precipitation mechanisms seem to be responsible for their formation.
In silician magnetites, excess electric charge brought by the replacement of ferric iron in tetrahedral site by silicon, could be compensated by the replacement of ferric iron in octahedral site by ferrous iron, known as γ–Fe2SiO4 component. The natural occurrence of silician magnetites, however, gives no positive support to the existence of this component at crustal pressures. Instead a preliminary Mössbauer experiment demonstrates that one silician magnetite has a maghemite –like structure by the omission of ferrous iron from octahedral site.  相似文献   

11.
Two bulk samples of clayey diatomite of Upper Miocene age originated from Western Macedonia, northern Greece and Thessaly central Greece were examined for their efficiency to be used as industrial absorbents. The samples were characterized using X-Ray Diffraction, Thermo-Gravimetric and Fourier Transform Spectroscopy, Scanning Electron Microscopy and ICP-MS analytical methods. The absorption capability of the clayey samples in oil and water were also examined. The mineralogy of both samples is predominated by the presence of clay minerals and amorphous silica. The clay minerals prevailed in the Klidi (KL) bulk sample, with muscovite being the dominant phase, and kaolinite and chlorite occurring in minor amounts. In the Drimos (DR) bulk sample, vermiculite was the predominant clay phase. Smectite was not found in either sample, whereas detrital quartz and feldspars were present in significant amounts. The amorphous silica phase (opal-A) occurs mainly with the form of disck-shaped diatom frustules. The chemistry of the samples is characterized by the predominance of silica, alumina, and iron, whereas all the other major and the trace elements are in low concentrations. Both clayey diatomite rocks exhibited sufficiently good oil and water absorption capacity, ranging between 70 to 79% in the clay-rich sample KL and 64 to 70% in the opal-A-rich sample DR. Comparing the properties of the rocks studied with other commercial absorbents, it is concluded that they may find applications as absorbents in industrial uses.  相似文献   

12.
煤系高岭土制取高纯氧化铝——萃取除铁   总被引：1，自引：0，他引：1  
煤系高岭土焙烧活化后与硫酸铵反应,水浸取得到硫酸铝铵溶液,再采用磷酸二异辛基酯(P204)-N,N-甲基庚乙酰胺(N503)混合萃取剂除铁;与碳酸氢铵共沉淀制取碳酸铝铵(AACH)结晶后热解煅烧,制得高纯超细氧化铝.讨论了用N503-P204混合萃取剂进行三级逆流萃取时,水相pH值和萃取时间等操作条件对萃铁效果的影响;用TG-DTA研究了前驱物的热解特性,用XRD、TEM表征了AACH及其煅烧产物的物相及粒径;用ICP测定了煅烧产物的纯度.分析结果表明,铁的萃取率达到99.2%,AACH的纯度满足制取高纯超细Al2O3的要求.产品为粒径小于70 nm、纯度大于99.95%的Al2O3.  相似文献   

13.
煤的结渣特性是动力用煤的主要指标,也是燃煤锅炉设计过程中的重要参数,煤灰中化学成分对煤灰熔融性和结渣性影响较大,尤其是SiO2、Al2O3、Fe2O3、CaO等主要成分的含量和组成。基于元屯沟井田三叠系瓦窑堡组煤的煤灰成分、煤灰熔融性试验数据分析,发现该区煤层中SiO2+Al2O3含量大于80%,Fe2O3+CaO小于10%,煤灰属较高灰煤灰软化温度。通过对煤灰软化温度、硅铝比、酸碱比、铁钙比、结渣指数以及综合结渣指数等多个指标的分析,得出煤灰属轻微结渣性。  相似文献   

14.
Green synthesis of nanomaterials has received increasing attention as an eco-friendly technology in materials science. Here, we have used two types of extractions from green tea leaf (i.e., total extraction and tannin extraction) as reducing agents for a rapid, simple and one-step synthesis method of mesoporous silica nanoparticles/iron oxide nanocomposite based on deposition of iron oxide onto mesoporous silica nanoparticles. Mesoporous silica nanoparticles/iron oxide nanocomposite were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray, vibrating sample magnetometer, N2 adsorption and high-resolution transmission electron microscopy. Mesoporous silica nanoparticles/iron oxide nanocomposite was used as a solid adsorbent for removal of lindane pesticide from aqueous solutions. The developed system possesses the advantages of silica as core that include large surface area and advantages of iron oxide (shell) that include the capability to interact with chlorinated compounds and ability to release by using external magnetic field. UV-Vis technique was used as a simple and easy method for monitoring the removal of lindane. Effects of pH and temperature on the removal efficiency of the developed mesoporous silica nanoparticles/iron oxide nanocomposite toward lindane pesticide were also investigated. Fourier transform infrared spectroscopy, high-performance liquid chromatography and gas chromatography techniques were used to confirm the high ability of mesoporous silica nanoparticles/iron oxide nanocomposite for sensing and the capture of lindane molecules with high sorption capacity (about 99%) that could develop a new eco-friendly strategy for detection and removal of pesticide and as a promising material for water treatment.  相似文献   

15.
In order to assess the importance of siliceous sediments as a sink for oceanic B and to determine the effect of diagenesis on the mobilization of B, samples were analysed from chert nodules, bedded cherts, and siliceous banded iron formations from a variety of sedimentary environments and geologic ages. Boron analyses on bulk samples were made by prompt gamma neutron activation analysis. The distribution of B in rocks was mapped using α-track methods.Nodular Phanerozoic cherts typically contain 50–150 ppm B, and bedded cherts somewhat less. The B is initially concentrated in tests of silica-secreting organisms, but some is lost in early diagenesis as silica progressively recrystallises to quartz.Banded iron formation silica of Archean and Proterozoic age usually contains < 2 ppm B. This conforms with the view that such silica is not of biogenic origin but, since many iron formations are undoubtedly of marine origin, raises the question whether Precambrian oceans were impoverished in B. Analyses of Precambrian marine argillaceous sediments, averaging 70 ppm B, do not resolve this question.  相似文献   

16.
Chemical and mineralogical analyses of the clay fraction of eleven soils containing a large amount of vermiculite clay and representing a wide range of parent materials revealed that two types of vermiculite clays exist: (1) An aluminous type in which Al3+ substitutes for Si4+ in tetrahedral positions in the same order of magnitude as in the coarse grained vermiculites and micas, and with Al3+ as the dominant octahedral ion. (2) A silicious type in which only Si4+ occupies the tetrahedral positions, and with Fe3+ and Mg2+ as the dominant octahedral ions. The aluminous vermiculite clay was found to occur in soils derived from acid igneous rocks and is usally associated with mica, whereas the silicious type was found to occur in soils derived from basic igneous rocks which do not contain mica. Because of this close association of these two types to their parent material, it was concluded that the aluminous vermiculite is a product of alteration of mica whereas the silicious type is a product of synthesis from primary oxides of silica, alumina, iron, and magnesium. Both types of vermiculite clays tend to be dioctahedral in contrast to the trioctahedral nature of the coarse-grained vermiculite.  相似文献   

17.
A geological survey carried out in the Yaoundé (Cameroon) region has revealed the presence of homogeneous clayey laterite in the upper part of a laterite cover on interfluves, thickest on hills (780–800 m altitude) where ferricrete is absent, and clayey heterogeneous hydromorphic material in valleys. We present in this paper the physical, mineralogical and geochemical properties of these occurrences and discuss their potential as raw material for pottery, manufacture of bricks and tiles. These clayey raw materials are mostly made up of fine particles (ranging from 55 to 60% clay + silt in the clayey laterite, more than 70% clay + silt in the clayey hydromorphic material). Their chemical composition is characterized by silica (<60% SiO2), alumina (<35% Al2O3) and iron (ranging from 3 to 14% Fe2O3). Their main clay minerals are disorganized and poorly crystallized kaolinites. The average limits of liquidity (44.56% versus 91.58%) and limits of plasticity (22.4 versus 45.93) revealed that clayey hydromorphic material has the greatest plasticity. The studied raw materials are suitable for making pottery as well as the manufacture of bricks and tiles. However, the high iron content in the clayey laterite (between 11 and 12% Fe2O3) prevents their efficient use in the manufacture of ceramics.  相似文献   

18.
Fly ash was used to prepare alumina and silica white, The 3 stages of the process are as follows: ammonium sulfate calcining, acid leaching and alkali dissolution. The optimum conditions for the experiments to determine are as follows: molar ratio of (NH4)2SO4/Al2O3 is 6, the calcining time is 2h, he H2SO4 concentration is 20%, the leaching temperature is 80℃ and dissolution duration is 2h, the ratio of solution and solid reaction material is 6 for ammonium sulfate calcining and acid leaching stage, reaction time 30min, ratio of liquid to ore 5∶1, alkali concentration 45% and reaction temperature 95 ℃for the alkali dissolution stage. Under these conditions, the total leaching efficiencies of Al2O3 and SiO2 are 78.86% and 95%, respectively. The quality of the main products alumina and silica white can meet the national standards of GB/T24487-2009 and GB10517-89, respectively.  相似文献   

19.
The structures of continental plates and of oceanic basins suggested by several seismologists are utilized to estimate the relative volumes of sial and sima in the earth's crust. It seems that sial of the composition of the average igneous rock constitutes fully 26% and perhaps as much as 43% of the total crust. This ratio is far higher than seems likely if the sial had been entirely derived through fractional crystallization of a basaltic magma. The relative paucity of intermediate rocks as compared with granite and gabbro in the crust points in the same direction. The tentative conclusion is reached that the sial owes a large part of its volume to some process other than fractional crystallization of basalt—possibly to the emanation of low-melting constituents such as water, silica, potassa, soda, and alumina directly from the mantle to the crust.Publication authorized by the Director, United States Geological Survey.  相似文献   

20.
The study area forms part of an emerging iron ore province of southern Cameroon. Geochemistry analyses reveal that the siliceous itabirite has a very simple chemical composition, with Fe2O3 and SiO2 representing more than 96 wt.% of the average composition; suggesting chemical precipitates of silica and iron. Low Al2O3 and TiO2 concentrations and a weak positive correlation between them point to a minor detrital component in the precipitated marine sediments. The Si/Al ratio (average 52.7) indicates the hydrothermal origin of the studied itabirite. The Al–Si discrimination diagram supports this interpretation through the plot of all data in the hydrothermal field. The studied samples have low iron content (about 39.32% Fe), high gangue content (40.97% SiO2 and 1.3 % Al2O3) and low concentration of the deleterious elements (0.16 % P and < 0.01% S). The main gangue mineral is silica which can be efficiently removed from iron ores during preparation of raw materials for the blast furnace process. According to commercial standards for crude iron ores, it may be concluded that the Zambi iron ores are a low‐grade magnetic ore that can be profitably exploited for the production of iron for steel production.  相似文献   

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